The present invention relates to apparatus for expanding the channel output capacity of a control device such as a programmer used in automated audio-visual performances. In particular, the present invention relates to apparatus for expanding the channel output capacity of a programmer by selectively energizing a plurality of channel expander devices.
A programmer is a device which controls the states of a plurality of output devices such as slide projectors, tape recorders, and so forth. Automatic audio-visual performances using output devices such as slide projectors and tape recorders are made possible by the programmer. The programmer automatically controls the output devices in accordance with a preselected program. The preselected program is stored in a storage medium such as a paper tape.
More specifically, the program is stored in the form of punched holes in the tape. The programmer includes a tape reader which electro-optically scans the tape and detects the presence of punched holes therein. For purposes of storing the program in the tape, the tape is divided into a fixed number of channels which run along the length of the tape and a fixed number of lines or "cues" running along the width of the tape. The tape reader scans a fixed number of tape cues per second. Depending upon the information to be stored in the program, different holes are punched in different combinations of tape cue channels. A typical programmer is described in detail in pending U.S. Application Ser. No. 486,805 filed July 9, 1974, entitled Programmer Expander for a Plurality of Devices and pending application Ser. No. 537,750, filed Dec. 31, 1974, entitled Method and Apparatus for Interrupting a Device for a Preselected Interval of Time, both of which are incorporated herein by reference. In general, the channel output capacity of the programmer severely limits the flexibility and effect of an audio-visual performance. In particular, the greatest number of output devices that a programmer can directly control is equal to the number of channels on the tape. In order to expand the channel output capacity of the programmer, the programmer may be connected to a channel expander device which controls the output devices in response to the information stored in the programmer tape. Such a channel expander device is disclosed in U.S. Application Ser. No. 486,805. Using such a channel expander device, the output of an eight channel programmer can be expanded to 40 channels.
Although the channel expander device greatly increases the flexibility and effect of an audio-visual performance by significantly increasing the channel output capacity of the programmer, only one channel expander device can be connected to the programmer. Consequently, the channel output capacity of the programmer in combination with the channel expander device, although permitting the control of a large number of output devices, may be of limited application in large scale performances which employ hundreds of output devices.
Obviously, by way of partial solution to the problem of limited channel output capacity, a channel expander device may be designed to provide sufficient output channel capacity to control the expected number of output devices employed in audio-visual performance. This approach, however, is somewhat self-limiting since, should the channel output capacity of the combined programmer and channel expander device be exceeded in the future, the system cannot be augmented by other channel expander devices to further increase the channel output capacity of the programmer. Instead, a channel expander device having still greater channel output capacity must be designed. Needless to say, the foregoing approach to solving the problem of limited programmer channel output capacity entails increasing complexity and cost.
The primary advantage of the present invention is that the channel output capacity of the programmer can be expanded without redesigning the channel expander devices.
Another advantage of the present invention is that it permits the interconnection of a plurality of existing channel expander devices in a simple and direct manner.
A still further advantage of the present invention is that it permits automatic control of a multitude of output devices without operator intervention.
Further advantages of the present invention will appear in the ensuing disclosure.